Machine adjustable boring bars have previously been suggested, and among the first types were ones where cutting edge tools could be interchanged as necessary to maintain a sharp cutting edge, but had only boring capabilities. Other machine adjustable boring bars have been proposed wherein a radial adjustment of the boring tool was possible, yet the tool holder was not interchangeable, i.e., it was generally a permanent part of the machine tool spindle. One of the prior known machines provided radial adjustment of the boring tool by means of a drive shaft, others suggested a longitudinally movable central rod for use in the radial adjustment of a boring tool, or an internal electric servo motor. A stylus and a contoured template were also employed for this purpose in one machine, while in another a contour cam was used in radial adjustment of a boring tool. A planetary gear has also been proposed for radial adjustment of a tool, with the input to the planetary gearing coming from the rotatable spindle.
In more recent years, many machine tools have been equipped with tool changing mechanisms to change tools from a magazine into the operating spindle. The radial adjustment of such a tool on an interchangeable tool holder has been suggested. In this case, the radial adjustment was by a longitudinally movable central rod in the machine tool spindle. Radial adjustment was also made by means of planetary gearing together with means to hold the ring gear stationary. In these latter devices, the one input to the planetary gearing was from the machine tool spindle, and only minor adjustments in radial position were established because the tool holder had a slot to establish an effective hinge portion to permit slight bending movements of the cutting tool mount.
In the past, radial adjustment of a cutting tool edge has had basically two different areas of application; first, compensating for the wear of a tool used in the manufacture of internal or external cylindrical surfaces, with the relatively small radial adjustment of the cutting edge occurring preferably when the tool is disengaged from the workpiece and, second, radial adjustment for the purpose of facing, taper turning or similar working processes, with the radial adjustment occurring during an engagement of the tool with the workpiece. It should be recognized that this list is not exhaustive and that there are other purposes for radial adjustment, however, the prior known devices sought to accomplish radial adjustment mainly for one or both of the two applications listed above.
Devices in which the tool is adjusted by adjusting, for a certain amount, an adjusting ring provided with a scale, when the work spindle is at rest are already known. In order to obtain a continuous tool adjustment during the working process, the adjusting ring is connected to a fixed point of the spindle housing through a separate linkage, so that it does not participate in the spindle rotation, such that the cross slide is adjusted independent from the spindle rotation through the transmission gear.
Numerically controlled contouring heads are also known for use with horizontal boring machines. Certain contour bores, grooves, faces, etc. can be machined without removing the workpiece from the machine, thereby eliminating additional set-ups, reducing overall cycle time, reducing inventory levels and, as a result, reducing the cost of the machining operation. Contour boring, taper boring, recessing, threading, facing, chamfering, turning and grooving are generally done on horizontal or vertical lathes. When the workpiece is too awkward to rotate, when a lathe is not available to do the work, or when milling, drilling and tapping on the same machine can avoid an extra set-up, the use of a numerically controlled contouring head on a horizontal boring machine can have significant advantages. Cross-feeding heads can be attached to the spindle sleeve of a horizontal boring machine. The typical horizontal boring machine allows for independent, parallel feeds of the spindle along a Z axis and the workpiece along a W axis. Radial motion is typically controlled by the Z axis feed motion of the spindle, providing numerically controlled radial feed on a rotating tool. The current contouring head configurations used to translate the longitudinal or axial feed of the spindle into radial feed of the rotating tool, are generally limited to boring, turning and threading. When these operations are completed the heads requires removal to do the other basic machining functions, such as milling, drilling, tapping, reaming, etc.. This head then is an attachment limited to special applications only.